MBMS (Multimedia Broadcast and Multicast Service) is a technique in which a base station of a mobile communication system, for example, effectively performs broadcast and multicast service of multimedia content, such as transmitting moving images and music to mobile stations. Services utilizing MBMS have been developed.
Multicast communication uses a technique of simultaneously completing communications with a plurality of mobile stations by one transmission. With this technique, radio waves can be efficiently used for the realization of service in which the same content is viewed by a plurality of users at the same time.
Since the MBMS is basically considering in known W-CDMA networks, an additional frequency band for broadcast data transmission is not required, that is, a function is merely added to known base stations for the MBMS. Accordingly, the MBMS is realized with ease (refer to Japanese Laid-Open Patent Publication No. 2004-208153, Japanese National Publication of International Patent Application No. 2007-504721, No. 2007-505914, No. 2007-536871, for example).
FIG. 12 illustrates a configuration of a base station (hereinafter sometimes referred to as an “evolved Node B” or an “eNB”) 1201 proposed for realizing the MBMS, configurations of a radio signal processing unit 1206, an interface unit 1204, and a call control unit 1205 which are included in the eNB, and a configuration of an MBMS controller (server) 1203.
In FIG. 12, the eNB 1201 is located between the MBMS controller 1203 and air interface 1212. Mobile stations (hereinafter sometimes referred to as “User Equipments” or “UEs”) 1202 are connected to the eNB 1201 via air interface 1212. The eNB 1201 relays MBMS data and call information between the MBMS controller 1203 and the UEs 1202.
The radio signal processing unit 1206, included in the eNB 1201, processes transmission signals and reception signals. It also transmits data to and receives data from the MBMS controller 1203 through the interface (IF) unit 1204, which is disposed between the radio signal processing unit 1206 and the MBMS controller 1203.
In the radio signal processing unit 1206, a downlink signal processing unit 1207 includes a control channel (CH)/data channel (CH) processing unit 1209 which performs channel processing for the MBMS and normal downlink processing.
The radio signal processing unit 1206 further includes an uplink signal processing unit 1208. The uplink signal processing unit 1208 includes a control CH/data CH processing unit 1210 which processes an uplink control channel and uplink communication data and an RACH (Random Access Channel) processing unit 1211 which processes an RACH.
In the MBMS, the same data supplied through the interface unit 1204 is simultaneously transmitted from the downlink signal processing unit 1207 to a plurality of UEs 1202.
FIG. 13 illustrates a sequence of transmission (i.e. delivery) of the MBMS data from the MBMS controller 1203 to the UEs 1202.
In step S1301, a transmission stop state in which transmission from the MBMS controller 1203 is stopped and the UEs 1202 transmit MBMS request signaling information to the MBMS controller 1203 using a control CH and a dedicated CH.
In step S1302, the receiving the request signaling information, the MBMS controller 1203 is brought to an MBMS transmission start state. In step S1303, the MBMS controller 1203 reads requested content from an MBMS data server and transmits the content to the UEs 1202 using an MBMS channel (MBMS CH) as MBMS service.
In step S1304, the UEs 1202 receive the transmitted MBMS service.
In a known MBMS, when the MBMS is started, each of the UEs 1202 transmits the request signaling information to the MBMS controller 1203. Therefore, a considerable period of time is required for processing the requests by the MBMS controller 1203, that is, a considerable period of time is required to enable the provisioning of the MBMS.
FIG. 14 illustrates a sequence of transmission when requests are transmitted from three UEs 1202-1 to 1202-3, and FIG. 15 illustrates a route of the requests. The three UEs 1202-1 to 1202-3 transmit requests to the MBMS controller 1203 through a control CH or a dedicated CH. As illustrated in FIG. 15, the requests are received by the control CH/data CH processing unit 1210 included in the uplink signal processing unit 1208 of the eNB 1201, and thereafter, transmitted to the MBMS controller 1203 through the IF unit 1204. As illustrated in FIG. 14, the MBMS controller 1203 performs MBMS-request accepting processing for individual requests transmitted from the UEs 1202. Since a considerable period of time is required for a request processing time 1401, a considerable period of time is required to provision the MBMS.
When the number of UEs 1202 increases, the processing capacity requirements of the MBMS controller 1203 is increased to accommodate the increased number of UEs 1202.
Furthermore, the UEs 1202 transmit request signaling information to the MBMS controller 1203 when the MBMS is started. The control CH/data CH processing unit 1210, included in the uplink signal processing unit 1208 of the eNB 1201, inserts communications performed by certain UEs 1202 which transmit MBMS signaling information into normal communications performed by the UEs 1202, using the control CH and the dedicated CH. Therefore, the number of UEs 1202 which perform normal communications is reduced, and communication speed for each UE 1202 is reduced.
Since MBMS signaling information embedded in the control CH or the dedicated CH is to be extracted, performance of reception processing of the control CH/data CH processing unit 1210 is preferably improved.